A high resolution silicon-on-glass Z Axis Gyroscope Operating at Atmospheric Pressure

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Description/Abstract

This paper describes a high-resolution silicon-on-glass $z$ axis gyroscope operating at atmospheric pressure. The mechanical structure is designed in such a way that it exhibits low cross coupling between drive and sense mode of less than 0.5% simulated using finite-element method and 1.35% verified by experimental measurements. Due to a symmetrically designed structure, the specified bandwidth can be maintained despite of fabrication imperfections. The fabrication process flow is based on a combination of silicon on glass bonding and deep reactive ion etching which results in a large proof mass and capacitances. A closed loop self-oscillation drive interface is used to resonate the gyroscope in the drive mode, which reaches steady-state after 150 ms. Using area-varying capacitors, large quality factors of 217 and 97 for drive and sense mode, respectively, were achieved operating at atmospheric pressure. A low drive voltage, with a 1 ${rm V}_{rm peak hbox{-}peak}$ AC drive amplitude and 10 V DC bias was used to excite the drive mode. The measured scale factor was 10.7 ${rm mV}/^{circ}/{rm s}$ in a range of ${pm 300}^{circ}/{rm s}$ with a $R ^{2}$-nonlinearity of 0.12%. The noise equivalent angular rate is 0.0015$^{circ}/{rm s}/{rm Hz}^{1/2} (=5.4^{circ}/{rm h}/{rm Hz}^{1/2})$ in a 50 Hz bandwidth. The measured SNR was 34 dB at an angular rate input signal with an amplitude of 12.5$^{circ}/{rm s}$ and a frequency of 10 Hz. Without any active temperature control, zero bias stability of 1 $^{circ}/{rm s}$ was achieved for long-term measurements over six hours and 0.3$^{circ}/{rm s}$ for short-term measurements over 120 seconds $(1-sigma)$.